From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id AFC67FCC04D for ; Fri, 6 Mar 2026 17:19:19 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 25CAC6B00B4; Fri, 6 Mar 2026 12:19:19 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 23DF16B00B7; Fri, 6 Mar 2026 12:19:19 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 15D486B00B8; Fri, 6 Mar 2026 12:19:19 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 03BA16B00B4 for ; Fri, 6 Mar 2026 12:19:19 -0500 (EST) Received: from smtpin14.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id C566D8C0AE for ; Fri, 6 Mar 2026 17:19:18 +0000 (UTC) X-FDA: 84516299196.14.C5CC780 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf18.hostedemail.com (Postfix) with ESMTP id 08AFA1C0007 for ; Fri, 6 Mar 2026 17:19:16 +0000 (UTC) Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=muO0cZ9r; spf=pass (imf18.hostedemail.com: domain of rppt@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=rppt@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1772817557; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=qtffwH0lS3IAKMv4Vt6FSD4IitP/Z7NlvAnyaQSDaB0=; b=OBXgDJsadQT/wxIyPWPOyLPSSncP0CPda91uhWjAFC1VDG690XP3ZvMOzsjXtQSzfyaPFb +FFizBJi6tZ5Z94LkDjmVWBBerx+hWeuaLmZ1BNmIEIOv8MwMMDoIFPx2zfBDMHoNIeTfi Pv2TGFNebJ9T1Op17kRZ0yBij3MuB4U= ARC-Authentication-Results: i=1; imf18.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=muO0cZ9r; spf=pass (imf18.hostedemail.com: domain of rppt@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=rppt@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1772817557; a=rsa-sha256; cv=none; b=ldMAZ5WWyqsF5srn8pbgQ82cCzqamEEWmkGwLcfdP8uiIvUN43GuG1Ihedi7x2f/Mpz91L lzINUbdrtmUgvjvAgJd2T86ioG9OqUMUL9EfcMPDjt2tzcdqYVVZ7U8oHyDN2841RgE4b6 Ow2s+hTGYaoufBBpG9PlufjXqPQnwOc= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 2F91944333; Fri, 6 Mar 2026 17:19:16 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4C953C19425; Fri, 6 Mar 2026 17:19:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772817556; bh=/0oNlg7fiYv022nxhnrVEoCU64mvQSwuS01zGUwLSsQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=muO0cZ9r+JBiL14XaQg5yw9LiQxGht59+apEgASJ2jR3LGxBAL2DsQtktz4uqSNqJ PkXHY04N+jL5v3G1MiqgSB6TbYGHqdBDSNAWY/aNjQxFtJSBEK0S22O0Y9wGNaJP17 In19HrRalevmDmNv5JBdAdSrm7ZCxnFnlXDD6srzq008AVs4fRuyfSBrSnPz+RHps5 1lQ+eH6EvtYxUo4N0NJqRwDFaYVUx8J7UuASQtNTGCIpna7WU5kGuspoZHDKNb5Pl7 dHZou2u+P4ijg57yiLXnqs07Bf41RlHmXBQ2PWIXWVKS2bD7DRkDLEXTYWCMpSCDpW ThUH3wtwpnBqA== From: Mike Rapoport To: Andrew Morton Cc: Andrea Arcangeli , Axel Rasmussen , Baolin Wang , David Hildenbrand , Hugh Dickins , James Houghton , "Liam R. Howlett" , Lorenzo Stoakes , "Matthew Wilcox (Oracle)" , Michal Hocko , Mike Rapoport , Muchun Song , Nikita Kalyazin , Oscar Salvador , Paolo Bonzini , Peter Xu , Sean Christopherson , Shuah Khan , Suren Baghdasaryan , Vlastimil Babka , kvm@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v2 08/15] shmem, userfaultfd: use a VMA callback to handle UFFDIO_CONTINUE Date: Fri, 6 Mar 2026 19:18:08 +0200 Message-ID: <20260306171815.3160826-9-rppt@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260306171815.3160826-1-rppt@kernel.org> References: <20260306171815.3160826-1-rppt@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 08AFA1C0007 X-Rspamd-Server: rspam07 X-Stat-Signature: bs6nji6kfk11jncnqcgg7aunksabfo76 X-Rspam-User: X-HE-Tag: 1772817556-147027 X-HE-Meta: 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 09RrZuCR gfI3ZBMzX4BpnHF5HoOIvEB2heRxdvV5g7Y/rK16EPERqJXLJ4fJJp5nMb6iq4fG6nHUFglQQ1qbTL06kVfQ+iwaApdVEzpaJVgxcTy+EgJ+r2XyrauPav2WyfKC3kZWiqnS7T4YtyNMVB3PpxifHfNMv9AptgMGvFE7sgqmNzwEManlSCv6RmA0WVa/nvbrAD4fuJWfCkaXery17xO4tP/xNWBwBeQSnV/s1ZW07W9a1LHVCSBvgCEe6su3FFhElhyV822B1ha1Ys9e7CtT7ChTMGA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: "Mike Rapoport (Microsoft)" When userspace resolves a page fault in a shmem VMA with UFFDIO_CONTINUE it needs to get a folio that already exists in the pagecache backing that VMA. Instead of using shmem_get_folio() for that, add a get_folio_noalloc() method to 'struct vm_uffd_ops' that will return a folio if it exists in the VMA's pagecache at given pgoff. Implement get_folio_noalloc() method for shmem and slightly refactor userfaultfd's mfill_get_vma() and mfill_atomic_pte_continue() to support this new API. Signed-off-by: Mike Rapoport (Microsoft) --- include/linux/userfaultfd_k.h | 7 +++++++ mm/shmem.c | 15 ++++++++++++++- mm/userfaultfd.c | 32 ++++++++++++++++---------------- 3 files changed, 37 insertions(+), 17 deletions(-) diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h index 56e85ab166c7..66dfc3c164e6 100644 --- a/include/linux/userfaultfd_k.h +++ b/include/linux/userfaultfd_k.h @@ -84,6 +84,13 @@ extern vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason); struct vm_uffd_ops { /* Checks if a VMA can support userfaultfd */ bool (*can_userfault)(struct vm_area_struct *vma, vm_flags_t vm_flags); + /* + * Called to resolve UFFDIO_CONTINUE request. + * Should return the folio found at pgoff in the VMA's pagecache if it + * exists or ERR_PTR otherwise. + * The returned folio is locked and with reference held. + */ + struct folio *(*get_folio_noalloc)(struct inode *inode, pgoff_t pgoff); }; /* A combined operation mode + behavior flags. */ diff --git a/mm/shmem.c b/mm/shmem.c index f2a25805b9bf..7bd887b64f62 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -3295,13 +3295,26 @@ int shmem_mfill_atomic_pte(pmd_t *dst_pmd, return ret; } +static struct folio *shmem_get_folio_noalloc(struct inode *inode, pgoff_t pgoff) +{ + struct folio *folio; + int err; + + err = shmem_get_folio(inode, pgoff, 0, &folio, SGP_NOALLOC); + if (err) + return ERR_PTR(err); + + return folio; +} + static bool shmem_can_userfault(struct vm_area_struct *vma, vm_flags_t vm_flags) { return true; } static const struct vm_uffd_ops shmem_uffd_ops = { - .can_userfault = shmem_can_userfault, + .can_userfault = shmem_can_userfault, + .get_folio_noalloc = shmem_get_folio_noalloc, }; #endif /* CONFIG_USERFAULTFD */ diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index b55d4a8d88cc..98ade14eaa5b 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -191,6 +191,7 @@ static int mfill_get_vma(struct mfill_state *state) struct userfaultfd_ctx *ctx = state->ctx; uffd_flags_t flags = state->flags; struct vm_area_struct *dst_vma; + const struct vm_uffd_ops *ops; int err; /* @@ -231,10 +232,12 @@ static int mfill_get_vma(struct mfill_state *state) if (is_vm_hugetlb_page(dst_vma)) goto out; - if (!vma_is_anonymous(dst_vma) && !vma_is_shmem(dst_vma)) + ops = vma_uffd_ops(dst_vma); + if (!ops) goto out_unlock; - if (!vma_is_shmem(dst_vma) && - uffd_flags_mode_is(flags, MFILL_ATOMIC_CONTINUE)) + + if (uffd_flags_mode_is(flags, MFILL_ATOMIC_CONTINUE) && + !ops->get_folio_noalloc) goto out_unlock; out: @@ -577,6 +580,7 @@ static int mfill_atomic_pte_zeropage(struct mfill_state *state) static int mfill_atomic_pte_continue(struct mfill_state *state) { struct vm_area_struct *dst_vma = state->vma; + const struct vm_uffd_ops *ops = vma_uffd_ops(dst_vma); unsigned long dst_addr = state->dst_addr; pgoff_t pgoff = linear_page_index(dst_vma, dst_addr); struct inode *inode = file_inode(dst_vma->vm_file); @@ -586,16 +590,13 @@ static int mfill_atomic_pte_continue(struct mfill_state *state) struct page *page; int ret; - ret = shmem_get_folio(inode, pgoff, 0, &folio, SGP_NOALLOC); + if (!ops) + return -EOPNOTSUPP; + + folio = ops->get_folio_noalloc(inode, pgoff); /* Our caller expects us to return -EFAULT if we failed to find folio */ - if (ret == -ENOENT) - ret = -EFAULT; - if (ret) - goto out; - if (!folio) { - ret = -EFAULT; - goto out; - } + if (IS_ERR_OR_NULL(folio)) + return -EFAULT; page = folio_file_page(folio, pgoff); if (PageHWPoison(page)) { @@ -609,13 +610,12 @@ static int mfill_atomic_pte_continue(struct mfill_state *state) goto out_release; folio_unlock(folio); - ret = 0; -out: - return ret; + return 0; + out_release: folio_unlock(folio); folio_put(folio); - goto out; + return ret; } /* Handles UFFDIO_POISON for all non-hugetlb VMAs. */ -- 2.51.0